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目的:探讨钙调神经磷酸酶(CaN)在耐力运动时骨骼肌纤维类型和大小转变中的作用。方法:雄性SD大鼠(150~200g)随机分成对照组和运动组。运动组大鼠进行6周无坡度跑台训练(20m/min~28m/min),并在第3周末进一步随机分成2组:运动+环孢素组,皮下注射环孢素(CSA,15mg/kg体重/day)3周;单纯运动组,注射等量生理盐水。各组大鼠第6周末取比目鱼肌和趾长伸肌,分别用SDS-PAGE电泳法和肌纤维ATP酶染色法测定肌球蛋白重链(MHC)组成比例和肌纤维横断面积,同时用比色法测CaN活性,并用Westernblotting法测CaN和活化T细胞核因子2(NFAT2)蛋白含量。结果:单纯运动组大鼠比目鱼肌MHCⅠ比例(93.4±6.0%)显著高于对照组(82.7±6.6%),而运动+环孢素组大鼠MHCⅠ比例(79.3±8.4%)无增加,但其Ⅰ型肌纤维横断面积显著小于对照组和单纯运动组(P<0.05)。单纯运动组大鼠趾长伸肌胞浆CaN活性及胞核NFAT2蛋白含量显著高于对照组(P<0.05),但纤维比例无显著改变(P>0.05);运动+环孢素组大鼠趾长伸肌肌原纤维蛋白浓度显著高于单纯运动组(P<0.05),且该组各型肌纤维横断面积均显著小于对照组和单纯运动组(P<0.05)。结论:CaN参与了耐力运动骨骼肌纤维类型和大小的调控,且具有肌肉特异性。
Objective: To investigate the role of calcineurin (CaN) in skeletal muscle fiber type and size transition during endurance exercise. Methods: Male SD rats (150 ~ 200g) were randomly divided into control group and exercise group. Exercise rats were randomly divided into 2 groups: exercise + cyclosporine and cyclosporine (CSA, 15 mg / d) for 6 weeks without slope treadmill training (20m / min ~ 28m / kg body weight / day) for 3 weeks. The rats in the exercise group were injected with the same amount of normal saline. At the end of 6th week, the soleus muscle and extensor digitorum longus were taken at the end of 6th week. The proportion of myosin heavy chain (MHC) and the muscle fiber cross-sectional area were determined by SDS-PAGE electrophoresis and myofibrillar ATPase staining respectively. The activity of CaN was measured, and the content of CaN and NFAT2 in activated T cells was detected by Western blotting. Results: Compared with control group, the proportion of MHCⅠ in soleus muscle of exercise group was significantly higher than that of control group (93.4 ± 6.0% vs 82.7 ± 6.6%, P <0.01), while MHCⅠ ratio of exercise + cyclosporine group was 79.3 ± 8.4% The type Ⅰ muscle fiber cross-sectional area was significantly smaller than the control group and simple exercise group (P <0.05). Cytosolic CaN activity and nuclear NFAT2 protein content in the extensor digitorum longissimus muscle of rats in the exercise group were significantly higher than those in the control group (P <0.05), but there was no significant difference in the proportion of fibers (P> 0.05) The extensor digitorum longus muscle fibrinogen concentration was significantly higher than the simple exercise group (P <0.05), and the type of muscle fiber cross-sectional area were significantly less than the control group and simple exercise group (P <0.05). CONCLUSION: CaN is involved in the regulation of the type and size of skeletal muscle fiber in endurance exercise and has muscle specificity.